Precut sizes: the cheat sheet

The precuts, from smallest to largest

All dimensions assume standard 42" to 44" wide quilting cotton. Pack counts vary by manufacturer — Moda popularized most of these names, and other brands use their own (a jelly roll is a "rolie polie" at Riley Blake, a "design roll" elsewhere) — but the cut sizes are consistent industry-wide.

• Mini charm: 2.5" × 2.5" squares, usually 42 per pack ≈ 0.17 yd of fabric
• Charm pack: 5" × 5" squares, usually 42 per pack ≈ 0.69 yd
• Jelly roll: 2.5" × WOF strips, usually 40-42 strips ≈ 2.9 yd
• Layer cake: 10" × 10" squares, usually 42 per pack ≈ 2.78 yd
• Fat eighth: 9" × 21" cut, sold in bundles = exactly ⅛ yd of fabric
• Fat quarter: 18" × 21" cut = exactly ¼ yd of fabric, the queen of precuts
• Half-yard cut: 18" × WOF = ½ yd

Fat quarter vs regular quarter: why the shape matters

A regular quarter yard is 9" across the full width of the bolt — a long skinny strip. A fat quarter is the same amount of fabric cut as 18" × 21": half the width, twice the height. Same area, radically different usefulness. From a fat quarter you can cut a 10" square, twelve 5" charms, or 42 2.5" mini charms; from a skinny quarter, that 10" square is impossible.

That's why patterns say "fat quarter friendly" as a selling point, and why FQ bundles are how most collections come home from the shop.

Yardage math that patterns actually use

When a pattern calls for total yardage and you're holding precuts, the conversions are area-based: piece area divided by the 1,512 square inches in a yard of 42" fabric. Four fat quarters equal a yard exactly. A 42-piece charm pack is about two-thirds of a yard. A full jelly roll is nearly three yards — which is why jelly roll race quilts finish as fast as they do.

One honest caveat: area math flatters small pieces. Ten charm squares are 0.165 yards on paper, but you can't cut a 6" block from them. Use conversions for counting your stash, not for substituting what a pattern explicitly requires.

Storing and counting precuts

Precuts keep best in their factory wrap or ribbon — unfolded jelly rolls never quite roll back. In your inventory, count them as pieces ("31 of 42 charms left") rather than converted yardage; the yardage total is a nice-to-know, but the piece count is what tells you whether the pattern is sewable tonight. YardKeep tracks precuts exactly this way: pieces first, yardage equivalence in the totals.